The purpose of this project is to better understand the processes of neoplasia and hyperplasia as they occur in the parathyroid glands and the C-cell of the thyroid. Studies on the alterations that occur in enzymatic processes of protein synthesis, and cytoplasmic organelles such as lysosomes will be evaluated. DNA stimulation and suppression with calcium ions will be studied in normal, hyperplastic and neoplastic parathyroid glands. These changes will be compared with changes in the ultrastructure and lysosomal activity of these glands. The nature and pathways of proparathyroid and parathyroid hormone synthesis and secretion will be studied to determine if this process is significantly altered in neoplastic and hyperplastic parathyroid glands. Similar studies will be undertaken on the C-cells of the thyroid which secrete thyrocalcitonin.